In the building of roadways and in particular superhighways, a desire has grown for median separators comprising virtually unbroken concrete barriers between the roadbeds in physical separation of vehicles from crossing from one flow of traffic to opposite moving flow of traffic in the event of accidents or sleeping drivers. Another object of such barriers is to reduce headlamp glare from the two adjacent parallel roadbeds. The devices for accomplishing the casting of the barriers are continuous casting devices which lay down the barriers in the manner of a continuously moving extruder. The machines operate without forms so that compaction, vibration, mixing, and preliminary curing is performed prior to the concrete being extruded from the machine. The barrier casting machines are similar in many respects to continuous forming machines for curbing and the like. such machines make the median barriers or separators practical and economic. If forms were required, the manual labor involved in the making and removal of forms would be too great and such separators would be economically impractical. the casting machines move continously and with a fairly high quality finish and with very little slump and uniform concrete quality. Where local mars do occur, they are easily observed and repaired unlike the repairs necessary when forms are removed only to find cured concrete with voids and poor finish.
However, in continuous highway casting of median barriers, two principal difficulties persist. As the extruder or continuous casting machine moves forward and changes grade, there are occasional peaks and valleys and occasional deviations from the horizontal plane across the top of the barrier as extruded. These occur at changes of grades or in local surface irregularities. These deviations are usually outside of the specification requirements for the barriers and a crew of men have heretofore been required to trail the extruder and manually adjust the peaks and valleys and manually relevel the upper surface. Such finishing requires extreme care so as not to disturb the concrete in its curing and so as not to cause the concrete to slump or deform. Continuous casting is represented generally in the U.S. Pat. Nos. 2,707,422 to Canfield and 3,108,518 to O'Connor, Jr., both directed to curbing type structures. The barrier formers are generally sized up from such devices and each comprise a self-moving carriage with levelling wheels and controls and a chute or hopper into which concrete mix or premixed concrete is poured. Compactor-vibrator-mixer provisions are included in such machines and semi-cured and slump resistant concrete exits from the extruder gate or head in the cross-section form sought. The barriers are generally conical in cross-section with an intermediate change in slope and generally flat or slightly crowned across the top. The base is relatively wide and is layed down slightly below grade. The upper surface is relatively narrow and rarely under 4 to 6 inches across. Thus, the barrier is a monolith broken at intervals by vertical cuts to provide expansion joints against an inserted asphaltic pad.
So far as known to the inventor, there are no attachments for barrier machines to achieve the purpose of the presently described structure and the present invention has been greeted favorably in the field for its reduction of labor and superior finish result. A device of this nature working in the corrosive and abrasive environment of concrete must be rugged and continuously dependable. Several early attempts at designing and building a suitable barrier levelling attachment by the inventor failed until the present structure came into being.
The principal object of the present invention is the presentation of a tool for attachment to barrier forming machines which avoids manual finishing while permitting constant adjustment to field conditions to assure a level and uniform barrier with good finish with good screed and trowel grade.
Another object is to build such a machine which is easy to clean and maintain in the field and which is ruggedly serviceable.
Still another object is to provide a means for adjusting a trailing chute which is easily accessible without interruption of continuous casting or forming of the barrier.
Other objects will be appreciated by those skilled in the art as the description proceeds.